Damping material resin compositions, damping materials, restraining-type damping members, and use thereof

ABSTRACT

An object of the invention is to provide a damping material resin composition which is great in loss tangent, exhibits outstanding damping properties and enables a damping material to retain its own shape. The invention provides a damping material resin composition comprising 100 parts by weight of a thermoplastic resin having a chlorine content of 20 to 70 wt. % and a weight average molecular weight of at least 400,000, and 100 to 1000 parts by weight of a chlorinated paraffin having a chlorine content of 30 to 75 wt. % and 12 to 50 carbon atoms. (Preferably, the chlorinated paraffin contains 10 to 70 wt. % of a chlorinated paraffin having a chlorine content of at least 70 wt. %.)

This application is a continuation-in-part application of International Application PCT/JP2004/019188 (not published in English) filed Dec. 22, 2004.

TECHNICAL FIELD

The present invention relates to damping members of the restraining type suited, for example, to use in houses, apartment buildings, office building and like residential buildings, expressway, elevated bridges, railroad tracks and various like structures, motor vehicles, railroad cars, vessels and various vehicles, and also in household electric appliances and office automation appliances, for diminishing the vibration or oscillation and noise to be produced, damping material resin compositions for preparing such damping members, and damping materials comprising the composition.

BACKGROUND ART

The loss modulus (E″) of a material as divided by the storage modulus (E′) thereof, i.e., loss tangent (tan 67 =E″/E′), has heretofore been used as an indicator of the damping properties of the material. The greater the loss tangent, the higher the vibration absorbing properties of the material. Damping materials are generally considered excellent when exceeding 1 in the value of loss tangent. However, further improvements in damping properties are desired, and there is a demand for materials which are over 3 in loss tangent.

In connection with the above, Patent Literature 1 discloses a damping material comprising a polymer having a polar group and a chlorinated paraffin or liquid rubber admixed with the polymer.

However, the disclosed material is about 1.3 to about 2.8 in loss tangent (tanδ) and is not always fully satisfactory in damping properties.

The research conducted by the present inventors has revealed that when an increased amount of chlorinated paraffin or liquid rubber is incorporated into the damping material in an attempt to improve the loss tangent, the resulting material becomes insufficient in strength to entail the likelihood that the damping material will encounter difficulty in retaining its shape, for example, if exposed to heat.

Patent Literature 1: JP1999-80562A1

DISCLOSURE OF THE INVENTION Problem to be Solved by the Invention

In view of the problem of the conventional damping materials, an object of the present invention is to provide a damping material resin composition and a damping material exhibiting high damping properties and suitable for diminishing vibration or oscillation, a damping member of the restraining type comprising the damping material, and the use thereof.

Means for Solving the Problem

As a first feature of the present invention, the invention provides a damping material resin composition comprising 100 parts by weight of a thermoplastic resin having a chlorine content of 20 to 70 wt. % and a weight average molecular weight of at least 400,000, and 100 to 1000 parts by weight, preferably 200 to 1000 parts by weight, of a chlorinated paraffin having a chlorine content of 30 to 75 wt. % and 12 to 50 carbon atoms.

The present invention provides, as a second feature thereof, a damping material resin composition comprising 100 parts by weight of a thermoplastic resin having a chlorine content of 20 to 70 wt. %, 200 to 1000 parts by weight of a chlorinated paraffin having a chlorine content of 30 to 75 wt. % and a number average carbon atom number of 12 to 50 and 300 to 1000 parts by weight of an inorganic filler.

The present invention provides, as a third feature thereof, a damping material resin composition comprising a thermoplastic resin having a chlorine content of 20 to 70 wt. % and a degree of crystallinity of at least 5 J/g as measured by DSC, and a chlorinated paraffin having a chlorine content of 30 to 75 wt. % and 12 to 50 carbon atoms.

The present invention provides, as a fourth feature thereof, a damping material resin composition according to any one of the first to third features of the invention wherein the chlorinated paraffin contains 10 to 70 wt. % of a chlorinated paraffin having a chlorine content of at least 70 wt. %.

The present invention provides, as a fifth feature thereof, a damping material comprising a damping material resin composition according to any one of the first to third features of the invention.

The present invention provides, as a sixth feature thereof, a damping laminate comprising a damping material according to the fifth feature of the invention, and a restraining member laminated to one surface of the damping material.

The present invention provides, as a seventh feature thereof, a damping member of the restraining type comprising a damping material according to the fifth feature of the invention, a restraining member laminated to one surface of the damping material, and an adhesive resin layer laminated to the other surface of the damping material.

The present invention provides, as an eighth feature thereof, a damping member of the restraining type according to the seventh feature of the invention wherein the difference between the glass transition temperature (hereinafter referred to as “Tg”) of the damping resin layer and the Tg of the adhesive resin layer is at least 10° C.

The present invention provides, as a ninth feature thereof, a damping member of the restraining type according to the seventh feature of the invention wherein a plasticizer migration preventing film is interposed between the damping resin layer and the adhesive resin layer so as to separate these layers, and the difference between the SP value of the film and the SP value of all components having a melting point of up to 80° C. and included among the components of the damping resin layer and the adhesive resin layer is at least 1.

The present invention provides, as a tenth feature thereof, a damping member of the restraining type according to the sixth feature of the invention wherein the restraining layer is coated with a primer at least over the surface thereof adjacent to the restraining resin layer.

The present invention provides, as an eleventh feature thereof, a damping structure wherein a restraining-type damping member according to the tenth feature of the invention is affixed to a rough surface of a vibrating or oscillating body.

The present invention provides, as a twelfth feature thereof, a tone improving structure for acoustic systems wherein a secondary sound deadening material comprising a damping laminate according to the sixth feature of the invention is affixed to at least one portion of a peripheral device of the acoustic system with the damping material of the damping laminate.

The present invention provides, as a thirteenth feature thereof, an acoustic system tone improving structure according to the twelfth feature of the invention wherein the damping material is affixed to the peripheral device of the acoustic system with a double-faced adhesive tape, with a plasticizer migration preventing film interposed between the damping material and the adhesive tape.

The present invention provides, as a fourteenth feature thereof, an acoustic system tone improving structure according to the twelfth feature of the invention wherein the damping material comprises a damping material resin composition at least 2.5 in the peak value of loss tangent (tan δ), and the restraining member is at least 1 GPa in modulus of longitudinal elasticity.

First, the first feature of the invention will be described in detail.

In the first feature of the invention, a thermoplastic resin is used which contains 20 to 70 wt. % of chlorine. Examples of such thermoplastic resins are those containing chloride, such as chlorinated polyethylene, polyvinyl chloride, chlorinated polyvinyl chloride and vinyl chloride-vinyl acetate copolymer.

When the thermoplastic resin contains less than 20 wt. % of chlorine, the resin is prone to crystallize and therefore increases in storage modulus (E′) excessively diminishes in loss tangent (tan δ) and is liable to exhibit lower damping properties. When the chlorine content is in excess of 70 wt. %, an excessively increased intermolecular force will result to entail an increased storage modulus (E′), diminished loss tangent (tan δ) and the likelihood of impaired damping properties. Accordingly, the thermoplastic resin should have a chlorine content of 20 to 70 wt. %, preferably 30 to 50 wt. %.

The thermoplastic resin may contain a substituent other than chlorine. Examples of substituents other than chlorine are cyano, hydroxyl, acetyl, methyl, ethyl, bromine atom, fluorine atom, etc. The content of substituent other than chlorine is preferably up to 5 wt. %, since an excessive substituent content is likely to result in insufficient damping properties.

The thermoplastic resin to be used according to the first feature of the invention is at least 400,000 in weight average molecular weight. If the weight average molecular weight is less than 400,000, the damping member to be obtained is liable to have difficulty in retaining its own shape. Although there is no particular upper limit for the weight average molecular weight, weight values in excess of 10,000,000 will entail impaired formability or moldability, possibly presenting difficulty in preparing damping materials.

The chlorinated paraffin for use in the first feature of the invention contains 30 to 75 wt. % of chlorine. If the chlorine content is outside this range, the paraffin exhibits impaired compatibility with the thermoplastic resin and is likely to entail lower damping properties.

The chlorinated paraffin has 12 to 50, preferably 14 to 35, carbon atoms on the average. If the number of carbon atoms is less than 12, bleed-out is prone to result in impaired damping properties with the lapse of time, whereas when the number is in excess of 50, an excessively high viscosity will result to make the composition difficult to handle.

One kind of chlorinated paraffin may be used singly, or at least two kinds of chlorinated paraffins, which are different in chlorine content or in the number of carbon atoms within the above corresponding range, may be used in combination.

Preferably, the damping material resin composition comprises, for example, a chlorine-containing high polymeric material having a chlorine content of 20 to 70 wt. %, and at least one chlorinated paraffin having 10 to 50 carbon atoms and a chlorine content of 30 to 70 wt. %. More preferably, the resin composition comprises a chlorine-containing high polymeric material having a chlorine content of 20 to 70 wt. %, and a mixture of a first chlorinated paraffin having 12 to 16 carbon atoms and a chlorine content of 30 to 75 wt. % and a second chlorinated paraffin having 20 to 50 carbon atoms and a chlorine content of 30 to 75 wt. %.

The use of two kinds of chlorinated paraffins which are different from each other in the number of carbon atoms gives a higher peak value of loss tangent (tan δ) and achieves a great improvement in damping properties.

It is desired that the proportion of the second chlorinated paraffin in the mixture of two paraffins be at least 40 wt. %, because the peak value of loss tangent (tan δ) can then be further raised and held so raised over a long period of time, and also because the chlorinated paraffins can be inhibited from bleeding out from the damping material.

When the proportion of the chlorinated paraffin in the damping material resin composition according to the first feature of the invention is less than 100 parts by weight, the material obtained fails to have outstanding damping properties with a high loss tangent (tan δ). If the proportion is in excess of 1000 parts by weight and when the composition is made into a damping material in the form of a sheet, film or the like, the material encounters difficulty in retaining its own shape. Accordingly, the proportion of the chlorinated paraffin should be 100 to 1000 parts by weight, preferably 200 to 800 parts by weight, per 100 parts by weight of the thermoplastic resin.

According to the first feature of the invention, the absolute value of the difference between the chlorine content of the thermoplastic resin and the chlorine content of the chlorinated paraffin [|(chlorine content of the thermoplastic resin)—(chlorine content of the chlorinated paraffin)|] is preferably up to 20 wt. %, more preferably up to 15 wt. %. If the absolute value of this difference is excessively great, it is likely that the thermoplastic resin and the chlorinated paraffin will become insufficient in compatibility.

When required, plasticizers other than the chlorinated paraffin may be admixed with the damping material resin composition. Examples of preferred plasticizers other than the chlorinated paraffin are phthalic acid esters, adipic acid esters, phosphoric acid esters, epoxidized polybutadiene, epoxidized fatty acid esters, trimellitic acid esters, pyromellitic acid esters, sebacic acid esters, citric acid esters, (meth)acrylic acid oligomers, (meth)acrylic acid ester oligomers, methacrylic acid esters, etc. Plasticizers of the phthalic acid type are desirable for inhibiting the bleed-out of chlorinated paraffins. These plasticizers may be used singly, or at least two of them may be used in combination. When plasticizers other than those of the phthalic acid type are to be used, it is desirable to use the plasticizer in combination with the phthalic acid-type plasticizer.

The plasticizer is used in an amount of up to 200 parts by weight, preferably up to 180 parts by weight, more preferably up to 100 parts by weight, per 100 parts by weight of the damping material resin composition. When the plasticizer is used in this range, bleed-out can be inhibited, with an improvement effectively achieved in damping properties.

The damping resin composition of the first feature of the invention may have other additives further incorporated therein in order to ensure improved moldability or formability, stability and damping properties in so far as the advantages of the invention will not be impaired. Examples of other additives are organotin compounds, metal soap and the like serving as thermal stabilizers, phenolic antioxidants, hindered amine photostabilizers, benzophenone, triazole and like UV absorbers, etc.

The second feature of the invention will be described.

The damping material resin composition according to the second feature of the invention comprises 100 parts by weight of a thermoplastic resin having a chlorine content of 20 to 70 wt. %, 200 to 1000 parts by weight of a chlorinated paraffin having a chlorine content of 30 to 75 wt. % and a number average carbon atom number of 12 to 50, and 300 to 1000 parts by weight of an inorganic filler.

The weight average molecular weight of the thermoplastic resin is not limited particularly, whereas if the weight is less than 400,000, the damping member to be obtained will encounter difficulty in retaining its own shape unless an increased amount of the inorganic filler is used. Although there is no particular upper limit for the weight average molecular weight, weight values in excess of 10,000,000 will entail impaired formability or moldability, possibly presenting difficulty in preparing damping materials.

The chlorinated paraffin to be used is the same as the one used in the first feature of the invention.

The inorganic filler to be used is one of the desired inorganic fillers already known and used in molding thermoplastic resins. Examples of such fillers are calcium carbonate, mica, talc, silica, alumina, titanium oxide, aluminum hydroxide, magnesium hydroxide, clay, zeolite, zinc borate, etc. Calcium carbonate and mica easily produce damping properties and are desirable.

The number average particle size of the inorganic filler, although not limited specifically, is preferably 0.1 to 100 μm, more preferably 0.5 to 50 μm because the filler of such size readily produces damping properties.

If the amount of the inorganic filler is less than 300 parts by weight per 100 parts by weight of the thermoplastic resin, the temperature at which the loss coefficient of the damping resin composition becomes maximum can not be made as high as is desired. When the amount is in excess of 1000 parts by weight, the damping material composition becomes excessively hard and difficult to handle and exhibits impaired damping performance. Accordingly, the amount is 300 to 1000 parts by weight, preferably 400 to 900 parts by weight, per 100 parts by weight of the thermoplastic resin.

The second feature of the invention is otherwise the same as the first.

The third feature of the invention will be described.

The thermoplastic resin providing the damping material resin composition according to the third feature has a degree of crystallinity of at least 5 J/g as measured by DSC (Differential Scanning Calorimetry). When the degree of crystallinity is les than 5 J/g, the resin composition is liable to flow at high temperatures during use. Although there is no upper limit for the degree of crystallinity, the crystallinity degree, if excessively high, is likely to lead to a high storage modulus, a diminished value of loss tangent and impaired damping properties. Accordingly, the degree of crystallinity is preferably up to 50 J/g.

The third feature of the invention is otherwise the same as the first.

The fourth feature of the invention provides a damping material resin composition according to any one of the first to third features of the invention wherein the chlorinated paraffin contains 10 to 70 wt. % of a chlorinated paraffin having a chlorine content of at least 70 wt. %.

When the total amount of the chlorinated paraffin contains 10 to 70 wt. % of a chlorinated paraffin having a chlorine content of at least 70 wt. %, the damping material obtained has improved adhesion. The improved adhesion is favorable in using the damping material as affixed to the desired article.

If the proportion of the chlorinated paraffin having a chlorine content of at least 70 wt. % is less than 10 wt. % in the total amount of the chlorinated paraffin, it is likely that the adhesion needed for long-term use will be insufficient. When the proportion is over 70 wt. %, excessively strong adhesion will make the material difficult to handle.

The fifth feature of the invention provides a damping material comprising a damping material resin composition according to any one of the first to third features of the invention.

The damping material can be obtained by making the damping material resin composition into a sheet, tape or film or into a suitable other shape by extrusion, pressing, rolling, injection molding or like method. Such a damping material may comprise a single layer or a plurality of layers.

The damping material is not particularly limited in shape insofar as it is so shaped as to be generally useful in houses, apartment buildings, office building and like residential buildings, expressway, elevated bridges, railroad tracks and various like structures, motor vehicles, railroad cars, vessels and various vehicles, and also in household electric appliances and office automation appliances. For example, the material is in the form of a sheet, tape, film or the like.

The sixth feature of the invention provides a damping laminate comprising a damping material according to the fifth feature of the invention, and a restraining member laminated to one surface of the damping material.

The restraining member is preferably one having a modulus of longitudinal elasticity of at least 1 GPa. The restraining member is made of a material which is preferably greater in modulus of longitudinal elasticity than the thermoplastic resin constituting the damping material. It is more preferable that the modulus of longitudinal elasticity be at least 10 GPa so as to produce a satisfactory damping effect.

Examples of materials for the restraining members are lead, iron, steels (inclusive of stainless steel), aluminum (including aluminum alloys) and like metal materials; concrete, gypsum plasterboards, marble, slates, sand plates, glass and like inorganic materials; polycarbonate, polysulfone and like bisphenol A-modified resins; poly(meth)acrylate and like acrylic resins; polyvinyl chloride resin, chlorinated polyvinyl chloride resin and like chlorine-containing resins; acrylonitrile-butadiene-styrene rubber and like rubber materials; polyethylene terephthalate, polyethylene naphthalate and like saturated polyesters; styrene resins; polyethylene, polypropylene and like olefin resins; nylon 6, nylon 66, Aramid (aromatic polyamide) and like polyamide resins; melamine resins; polyimide resins; urethane resins; dicyclopentadiene, Bakelite and like thermosetting resins; wood, paper and like cellulosic materials; and plates or sheets of chitin, chitosan and the like.

These restraining members may be used singly, or at least two of them are usable in combination. The restraining member may be reinforced with glass fiber, carbon fiber, liquid crystal material, etc. The member may be in the form of a composite plate made of different materials, or may be an expanded body of such a material.

When waterproof, the restraining member is suited to give improved waterproof properties to soundproof conveyors for outdoor use.

The restraining member is preferably in the form of a sheet. In the case of restraining metal members, it is desirable to subject the member to a corrosion inhibiting treatment as by plating or coating. The restraining member may be made rough-surfaced or have perforations or be made from an inorganic material. When to be made, perforations may be about 3 to about 20 mm in diameter so as not to be clogged with dirt or soil, or so as not to permit penetration of water. Even when vibrated or oscillated, the restraining member tends to produce an enhanced soundproof effect owing to the surface roughness or perforations given insofar as the modulus of longitudinal elasticity is not impaired greatly.

The damping material in the form of a sheet and the restraining member may have a desired thickness. The sheet of damping material is preferably 0.1 to 5 mm in thickness. The restraining member is preferably 0.05 to 5 mm in thickness. In the case of hard restraining members having a modulus of longitudinal elasticity of at least 10 GPa, the restraining members are preferably 0.05 to 2 mm in thickness.

The damping material prepared from the damping material resin composition is capable of efficiently converting vibration energy to thermal energy owing to internal rotation of the thermoplastic resin and has high damping properties while retaining its own shape. The material has high transparency that is less susceptible to impairment because the chlorinated paraffin is not prone to bleed out or cohere owing to ultraviolet rays even if the material is used outdoors.

The seventh feature of the invention provides a damping member of the restraining type comprising a damping material according to the fifth feature of the invention, a restraining member laminated to one surface of the damping material, and an adhesive resin layer laminated to the other surface of the damping material.

The damping material and the restraining member may be those described with reference to the sixth feature of the invention.

The adhesive resin layer may preferably comprise a resin composition wherein an acrylic, polyolefin, butyral, urethane, rubber, silicone compound or the like is used as its base.

The adhesion of the adhesive resin layer is preferably at least 2 N/cm, more preferably 5 N/cm, as measured by the 180° C. peel test according to JIS Z 0237. The adhesive resin layer has a thickness which is preferably up to 2 mm, more preferably up to 1.5 mm, so as to diminish the influence on the peak temperature of the loss coefficient (η).

The eighth feature of the invention will be described.

If it is attempted to cause the peak of loss tangent (tan δ) which is to be used as an indicator of the performance of the damping member to appear approximately at room temperature, the glass transition temperature (hereinafter referred to as “Tg”) of the damping member resin also nearly approaches room temperature, so that sufficient adhesion becomes unavailable at low temperatures. The resin therefore has the problem that it is not usable, for example, outdoors during winter.

We have conducted intensive research in an attempt to overcome this problem and found that when the layer of damping resin is provided with an adhesive resin layer which is lower than the resin layer in glass transition temperature, high adhesion can be obtained even at low temperatures, with the peak temperature of the damping performance held around room temperature.

The eighth feature of the invention provides a damping member of the restraining type according to the seventh feature of the invention wherein the difference between the Tg of the damping resin layer and the Tg of the adhesive resin layer is at least 100° C.

If the difference between the Tg of the damping resin layer and the Tg of the adhesive resin layer is less than 10° C., the adhesive resin layer fails to exhibit satisfactory adhesion at room temperature. The Tg difference is preferably at least 15° C., more preferably at least 20° C.

The ninth feature of the invention provides a damping member of the restraining type according to the seventh feature of the invention wherein a plasticizer migration preventing film is interposed between the damping resin layer and the adhesive resin layer so as to separate these layers, and the difference between the solubility parameter (hereinafter referred to as the “SP value”) of the film and the SP value of all components having a melting point of up to 80° C. and included among the components of the damping resin layer and the adhesive resin layer is at least 1.

When the difference between the SP value of the plasticizer migration preventing film and the SP value of the liquid components of the damping resin layer and the adhesive resin layer is less than 1, it is likely that the plasticizer present in the damping resin layer and the adhesive resin layer will migrate. The SP value difference is preferably at least 1.5, more preferably at least 1.8. The film having such an SP value is preferably a PET film. The plasticizer migration preventing film is preferably at least 5 μm, more preferably at least 12 μm, in thickness.

The restraining-type damping members according to the seventh to ninth features of the invention are especially useful when made from the damping material resin composition of the second feature of the invention.

The tenth and eleventh features of the invention will be described.

If the strength of adhesion between the restraining layer and the damping resin layer is low, separation will occur at the interface between these layers when the damping member is adhered to a rough-surfaced vibrating or oscillating body. Restraining-type damping members are desirable wherein separation is unlikely to occur at the interface between the restraining layer and the damping resin layer when the damping member is affixed to the rough-surfaced oscillating body.

The tenth feature of the invention provides a damping member of the restraining type according to the sixth feature of the invention wherein the restraining layer is coated with a primer at least over the surface thereof adjacent to the restraining resin layer.

The primer coating is provided on the restraining member at least over the surface thereof adjacent to the restraining resin layer. The primer may be of the acrylic, polyester, polyvinyl chloride, butyral, vinyl chloride-vinyl acetate copolymer, cellulose, rubber, epoxy, urethane, melamine, silicone or like type. It is desired that the difference between the solubility parameter (SP value) of the primer and the SP value of the -damping resin layer be up to 1.5. When this SP difference is excessively great, it is impossible to ensure satisfactory adhesion strength between the restraining layer and the damping resin layer.

The eleventh feature of the invention provides a damping structure wherein a restraining-type damping member according to the tenth feature of the invention is affixed to a rough surface of a vibrating or oscillating body.

The restraining member for use in the eleventh feature of the invention is, for example, an aluminum plate having a thickness of 0.05 to 1.0 mm (more preferably a thickness of 0.1 to 0.3 mm).

The twelfth feature of the invention will be described.

Acoustic systems for use in motor vehicles are made ever sophisticated and improved in performance. The rider of the vehicle is caused to hear sound which is impaired in tone as compared with the inherent sound of the acoustic system by being influenced by secondary sound resulting from the original sound of the system (for example, upon impinging on interior portions of the vehicle) and by the vibration of the vehicle. Accordingly, JP1993-9095U proposes a damping member for substituting a bracket for mounting a speaker thereon, as a structure for giving improved tone.

The tone improving structure disclosed in the patent publication has the problem that it is not applicable to systems wherein the specified bracket is not used as a member for supporting the speaker. The use of the damping member which is excellent in attenuating effect mitigates the noise due to vibration but is not fully effective for suppressing the secondary sound (e.g., harmonics) resulting from the original sound of the acoustic system in the vehicle. Thus, the structure fails to fully contribute to improvements in the tone of vehicle acoustic systems.

It is desired to provide a tone improvement structure for acoustic systems which is adapted to improve the tone of the system by suppressing the secondary sound.

The twelfth feature of the invention provides a tone improving structure for acoustic systems wherein a secondary sound deadening material comprising a damping laminate according to the sixth feature of the invention is affixed to at least one portion of a peripheral device of the acoustic system with the damping material of the damping laminate.

The thirteenth feature of the invention provides an acoustic system tone improving structure according to the twelfth feature of the invention wherein the damping material is affixed to the peripheral device of the acoustic system with a double-faced adhesive tape, with a plasticizer migration preventing film interposed between the damping material and the adhesive tape.

The fourteenth feature of the invention provides an acoustic system tone improving structure according to the twelfth feature of the invention wherein the damping material providing the laminate comprises a damping material resin composition at least 2.5 in the peak value of loss tangent (tan δ), and the restraining member is at least 1 GPa in modulus of longitudinal elasticity.

According to the twelfth to fourteenth features of the invention, the term “peripheral device” refers to devices such as a door, floor, ceiling, bonnet, trunk, fender, pillar, rear mount, dashboard or the like, to which the speaker of the acoustic system for use in vehicles is to be attached. Such devices include a system accommodating board, rack and other peripheral devices for use with interior acoustic systems.

The damping material may be the one described with reference to the fifth feature of the invention. The restraining member may be the one described with reference to the sixth feature of the invention.

Preferably, the damping material is in the form of a sheet and has a loss coefficient of at least 0.15 as measured according to JIS G 0602 “Centrally Supported Steady State Vibrating Method” at 20° C., with the sheet material affixed to the entire area of one surface of an SPC steel panel measuring 250 mm in length, 20 mm in width and 1.6 mm in thickness.

It is desired that the damping material resin composition according to the first to third features of the invention comprise a resin which is at least 2.5 in the peak value of loss tangent (tan δ) as measured at 50 Hz.

The method of making the damping material from the damping material resin composition is the same as according to the first feature of the invention. The resulting sheet is cut to a required size for use in providing the tone improving structure for acoustic systems.

The sheet of damping material and the restraining member may have a desired thickness. However, when having too small a thickness, the damping material or the restraining member is low in tone improving effect. When having an excessive thickness, the material or member is excessive in weight and will not be workable easily. Accordingly, the sheet of damping material is preferably 100 μm to 10 mm in thickness, and the restraining member is preferably 50 μm to 10 mm in thickness. In the case of hard restraining members having a modulus of longitudinal elasticity of at least 100 GPa, the thickness is preferably 50 μm to 2 mm.

The resin composition containing a chlorinated paraffin has suitable adhesion and is easy to use or apply in affixing a secondary sound deadening sheet. The secondary sound deadening sheet may of course be secured in place, for example, with an adhesive tape.

To ensure the ease of application, it is desirable to affix a double-faced adhesive tape to the damping material (over the entire surface thereof not having the restraining member affixed thereto), with a plasticizer migration preventing film interposed therebetween.

The plasticizer migration preventing film is a thermoplastic film (such as PET film) which is at least 1 different in SP value from the plasticizer such as chlorinated paraffin. When having an excessive thickness, the film is not easy to use, whereas if having too small a thickness, the film will not be fully effective for the migration of the plasticizer. The thickness is therefore preferably 5 to 100 μm.

The double-faced adhesive tape is, for example, an acrylic adhesive agent which basically comprises a nonwoven fabric. The adhesion of the tape is preferably at least 5 N/cm (according to JIS Z 0237). The tape is preferably up to 0.2 mm in thickness since an excessive thickness will impair the work of applying the damping material.

The double-faced adhesive is affixed to the sheet of damping material with the plasticizer migration preventing film interposed therebetween. This assures ease of work, prevents the migration of the plasticizer of the damping material sheet and maintains the tone improving effect for a prolonged period of time.

The tone improving structure according to the twelfth feature of the invention for use with acoustic systems may be made by any desired method. However, to assure the ease of application work, it is desirable to prepare a secondary sound deadening sheet of slightly increased size in advance by affixing a restraining member to a sheet of damping material first and affixing a double-faced adhesive tape to the damping material sheet over the entire area of the surface thereof having no restraining member affixed thereto, to cut the sound deadening sheet in conformity with the area of the main body of the acoustic system or a peripheral device thereof, and to thereafter affix the damping material sheet to the system body or peripheral device in intimate contact therewith directly or with the adhesive tape positioned therebetween. The secondary sound deadening sheet comprising a sheet of damping material sheet and a restraining member may comprise a multiplicity of layers.

When the secondary sound deadening sheet is to be used for the tone improving structure for vehicle acoustic systems, the sheet is affixed, for example, to a door comprising a steel panel (composed of two panels, i.e., an outer panel and an inner panel) and a lining, at at least one portion of the steel panel of the door. In view of the ease of application work, the secondary sound deadening sheet is affixed preferably to the approximate entire area of the interior surface of the inner panel (i.e., the surface thereof adjacent to the lining). In view of a reduction of the noise due to vibration, the sheet is affixed, preferably to the inside surface of the outer panel corresponding to the rear side of the speaker. In this case, it is desired that the damping material sheet be prevented from slipping down when exposed to a high temperature since the door of the motor vehicle will readily become heated to a high temperature of about 80° C. From this viewpoint, it is desirable that the damping material resin composition preferably have incorporated therein 100 to 1000 parts by weight, more preferably 200 to 600 parts by weight, of calcium carbonate per 100 parts by weight of the composition. Further to give the restraining member such properties as to easily extend along the door panel which is curved, the member is preferably 1 to 100 GPa in modulus of longitudinal elasticity. Such a restraining member is, for example, a thin aluminum plate having a thickness of 0.05 to 1.0 mm, (more preferably a thickness of 0.1 to 0.3 mm).

Advantages of the Invention

According to the first feature of the invention, the chlorine and the degree of crystallinity of the thermoplastic resin, and the chlorine content of the chlorinated paraffin are in good balance, and the composition is not prone to flow at high temperatures. The damping material prepared from the composition therefore exhibits high damping properties while retaining its own shape satisfactorily.

According to the second feature of the invention, the addition of an inorganic filler enables the damping member to have a maximum value of loss coefficient at a temperature approximate to room temperature while permitting the damping material resin composition to have a maximum value of loss tangent at a temperature not higher than room temperature. The composition is accordingly easy to handle at low temperatures, enabling the material and member to exhibit high damping properties.

The third feature of the invention provides a damping material resin composition exhibiting high damping performance and favorably usable under the condition of high temperatures without flowing or slipping down. For this reason, the composition is suited to outdoor use involving direct exposure to sunlight and usable in household electric appliances and industrial devices as positioned close to a heat source.

According to the fourth feature of the invention, chlorinated paraffin serves to remarkably ensure the advantages of the first to third features of the invention and gives the damping material improved adhesion so as to render the material favorable to use as affixed to a desired article.

According to the fifth and sixth features of the invention, the damping material is easy to handle at low temperatures and exhibits excellent damping properties at room temperature. The material is therefore favorably usable in houses, apartment buildings, office building and like residential buildings, expressway, elevated bridges, railroad tracks and various like structures, motor vehicles, railroad cars, vessels and various vehicles, and also in household electric appliances and office automation appliances, for diminishing the vibration or oscillation and noise to be produced.

The seventh feature of the invention provides a damping member of the restraining type comprising a damping material, a restraining member and an adhesive resin layer.

The eighth feature of the invention maintains the peak temperature of damping performance approximately at room temperature and enables the adhesive resin layer to exhibit satisfactory adhesion even at low temperatures so as to ensure trouble-free application work, for example, outdoors during winter.

The ninth feature of the invention reliably prevents the migration of the plasticizer contained in the damping resin layer and the adhesive resin layer to maintain the damping properties and adhesive properties over a prolonged period of time.

The tenth feature of the invention reliably prevents separation from occurring at the interface between the restraining layer and the damping resin layer even if the restraining-type damping member is affixed to a rough-surfaced vibrating or oscillating body.

The eleventh feature of the invention effectively diminishes vibration and noise in various vibrating bodies.

According to the twelfth to fourteenth features of the invention, the tone improving structure can be installed without being influenced in any way by the shape of the main bodies of various acoustic systems or by the construction of mount members, and is capable of greatly improving tone by suppressing secondary sound which has not been conventionally taken into consideration and reproducing the original sound with fidelity.

BEST MODE OF CARRYING OUT THE INVENTION

The present invention will be described below in detail with reference to Examples and Comparative Examples. However, the invention is not limited to Examples given below.

EXAMPLE 1

A resin composition was prepared from 100 parts by weight of a chlorinated polyethylene (“ELASREN 351MA,” product of Showa Denko K.K., 500,000 in weight average molecular weight, 35 wt. % in chlorine content, hereinafter referred to as “CPE 1”) and 400 parts by weight of a chlorinated paraffin [“ENPARA K50,” product of Ajinomoto Fine Chemical Co., Ltd., 50 wt. % in chlorine content, 14 in average carbon atom number (containing at least 99% of compound having 12 to 50 carbon atoms), hereinafter referred to as “Enpara 1”]. The materials were kneaded at 100° C. using a roll kneader, and the composition was pressed at 120° C. to obtain a sheet of damping material having a thickness of 1000 μm.

EXAMPLE 2

A resin composition was prepared from 100 parts by weight of CPE 1, 400 parts by weight of Enpara 1 and 300 parts by weight of a chlorinated paraffin [“ENPARA 70,” product of Ajinomoto Fine Chemical Co., Ltd., 70 wt. % in chlorine content, 26 in average carbon atom number (containing at least 99% of compound having 12 to 50 carbon atoms), hereinafter referred to as “Enpara 2”]. The materials were kneaded at 100° C. using a roll kneader, and the composition was pressed at 120° C. to obtain a sheet of damping material having a thickness of 1000 μm.

EXAMPLE 3

A resin composition was prepared from 100 parts by weight of a chlorinated polyethylene (1,000,000 in weight average molecular weight, 40 wt. % in chlorine content, hereinafter referred to as “CPE 2”) obtained by post-chlorinating a high-density polyethylene by the water suspension process, and 600 parts by weight of Enpara 1. The materials were kneaded at 100° C. using a roll kneader, and the composition was pressed at 120° C. to make a sheet of damping material having a thickness of 1000 μm.

EXAMPLE 4

CPE 2 (100 parts by weight), 600 parts by weight of Enpara 1 and 200 parts by weight of Enpara 2 were kneaded at 100° C. using a roll kneader to prepare a resin composition, which was pressed at 120° C. to make a sheet of damping material having a thickness of 1000 μm.

COMPARATIVE EXAMPLE 1

A resin composition was prepared from 100 parts by weight of a chlorinated polyethylene (“ELASREN 401A,” product of Showa Denko K.K., 300,000 in weight average molecular weight, 40 wt. % in chlorine content, hereinafter referred to as “CPE 3”) and 100 parts by weight of a chlorinated paraffin [“TOYOPARAX” product of Tosoh Corp., 40 wt. % in chlorine content, 26 in average carbon atom number (containing at least 99% of compound having 12 to 50 carbon atoms), hereinafter referred to as “Enpara 3”]. The materials were kneaded at 100° C. using a roll kneader, and the composition was pressed at 120° C. to obtain a sheet of damping material having a thickness of 1000 μm.

COMPARATIVE EXAMPLE 2

A resin composition was prepared from 100 parts by weight of a chlorinated polyethylene (“ELASREN 402NA,” product of Showa Denko K.K., 200,000 in weight average molecular weight, 40 wt. % in chlorine content, hereinafter referred to as “CPE 4”) and 400 parts by weight of Enpara 1. The materials were kneaded at 100° C. using a roll kneader, and the composition was pressed at 120° C. to obtain a sheet of damping material having a thickness of 1000 μm, but it was impossible to deliver the resulting material from the press, as held in the form of a sheet. Thus, the damping material failed to retain its own shape.

The damping materials obtained in Examples 1 to 4 and Comparative Example 1 were evaluated by the following methods as to the peak value and peak temperature of loss tangent (tan δ) and adhesion. Table 1 shows the result of evaluation.

[Loss Tangent]

Using a viscoelasticity spectrometer (product of Iwamoto Seisakusho Co., Ltd.), the sheet of damping material prepared was checked for loss elastic modulus in tension under the conditions of measuring frequency of 50 Hz, sample length of 15 mm and strain of 20 μm over a measuring temperature range of −50 to 5° C., with the temperature raised at a rate of 30° C./min. The loss tangent (tan δ) was calculated by dividing the loss elastic modulus in tension (E′) by the storage elastic modulus in tension (E′) to determine the peak value and peak temperature.

[Adhesion]

An adhesion measuring device (“Tack Tester,” product of Island Kogyo Co., Ltd.) was used for the sheet of damping material prepared to measure a maximum value of force required for peeling off the measuring member under the conditions of the diameter of the measuring member of 12 mm and measuring temperature of 23° C. TABLE 1 Material characteristics Wt. avg. Avg. C Chlorine molecular atom content Proportion and result of evaluation weight number (%) Ex. 1 Ex. 2 Ex. 3 Ex. 4 Comp. Ex. 1 Comp. Ex. 2 CPE 1 500,000 — 35 100 100 — — — — CPE 2 1,000,000 — 40 — — 100 100 — — CPE 3 300,000 — 40 — — — — 100 — CPE 4 200,000 — 40 — — — — — 100 Enpara 1 — 14 50 400 400 600 600 — 400 Enpara 2 — 26 70 — 300 — 200 — — Enpara 3 — 26 40 — — — — 100 — Loss tangent Peak value 4.0 4.1 5.1 4.9 1.5 Unmeasurable Peak temp. (° C.) −5.2 10.8 −7.8 3.2 −5.4 Unmeasurable Adhesion (N) 17.7 49.0 22.6 46.1 14.7 Unmeasurable

Table 1 reveals that the damping materials of Examples 1 to 4 had a high value of loss tangent (tan δ) of over 3 and satisfactorily retained their own shape. In contrast, the material of Comparative Example 1 was low in loss tangent, failed to retain its own shape of sheet and was unable to afford any loss tangent measurement.

EXAMPLE 5, 6 and COMPARATIVE EXAMPLE 3-6

A damping material resin composition was prepared by feeding a chlorinated polyethylene (trade name “ELASREN 401A,” product of Showa Denko K.K., 40 wt. % in chlorine content), chlorinated paraffin (trade name “ENPARA K50,” product of Ajinomonto Fine Chemical Co., Ltd., 14 in number average carbon atom number, 50 wt. % in chlorine content), calcium carbonate (trade name “R JUTAN,” product of Maruo Calcium Co., Ltd., 7.3 μm in number average particle size) and thickener (trade name “ARKON M90,” product of Arakara Chemical Industries, Ltd.) in specified amounts listed in Table 2 to a roll kneader and kneading the materials at 100° C. The composition was pressed at 120° C. to obtain a sheet of damping material having a thickness of 1000 μm.

The sheet of damping material was laminated to an SPC steel panel (0.3 mm in thickness, 250 GPa in modulus of longitudinal elasticity) to obtain a damping laminate.

The sheets of damping materials and the damping laminates obtained in Examples 5 and 6, and Comparative Examples 3 to 6 were evaluated by the following methods with respect to the peak value of loss tangent (tan δ) and loss coefficient.

Table 2 shows the result of evaluation.

(1) Loss Tangent

The sheet of damping material prepared was fed to a viscoelasticity spectrometer (product of Iwamoto Seisakusho Co., Ltd.) for measurement under the conditions of measuring frequency of 50 Hz, sample length of 15 mm and strain of 20 μm over a measuring temperature range of −50 to 50° C., with the temperature raised at a rate of 3° C./min. The loss tangent (tan δ) was calculated by dividing the value obtained of loss elastic modulus in tension (E″) by the storage elastic modulus in tension (E′) to determine the peak temperature.

(2) Loss Coefficient

The damping laminate was laminated to a base (SPC steel panel measuring 1.6 mm in thickness, 20 mm in width and 250 mm in length) for use as a sample for measuring the loss coefficient. The central portion of the sample was attached to an electromagnetic vibrator (trade name “512D,” product of EMIC and subjected to vibration with band noise every 3° C. in the temperature range of 0 to 40° C. to measure the force and acceleration and plot a resonance curve of the centrally excited vibration method. The loss coefficient was calculated from the half-value width of the primary and secondary antiresonance peaks thereof, and the maximum temperature of the loss coefficient was taken as the peak temperature. The loss coefficient at 20° C. was also determined.

(3) Peak Temperature Difference

The difference between the peak temperature of the loss coefficient and the peak temperature of the loss tangent was calculated.

(4) Handleability at Low Temperatures

The 1000-μm-thick sheet of damping material obtained was affixed to an SPC steel panel and evaluated according to the following criteria.

-   ∘. . . fully adhered. -   X . . . failed to adhere.

X X . . . sheet collapsed to remain unshaped. TABLE 2 Example Comparative Example 5 6 3 4 5 6 Damping material resin composition Chlorinated ethylene resin 100 100 100 100 100 100 Chlorinated paraffin 400 400 400 400 400 400 Calcium carbonate 400 800 — 200 — 1200 Thickener — — — — 100 — Physical properties Loss tangent peak temp. (° C.) 4.0 4.0 4.0 4.0 16.0 7.0 Loss coefficient peak temp. (° C.) 15.0 21.0 3.0 9.0 15.0 27.0 Peak temp. difference (° C.) 11.0 17.0 −1.0 5.0 −1.0 20.0 Loss coefficient at 20° C. (—) 0.36 0.42 0.09 0.15 0.37 0.12 Handleability at low temp. ◯ ◯ ◯ ◯ X XX

Table 2 reveals that the damping materials of Comparative Examples 3 to 6 are not desirable since the difference between the temperatures representing the maximum value of the loss tangent and that of the loss coefficient is small to result in impaired damping properties at room temperature around 20° C. or lower handleability at low temperatures.

On the other hand, the damping materials of Examples 5 and 6 are suitable as such; the difference between the temperatures representing the maximum value of the loss tangent and that of the loss coefficient is great, the resin remains unhardened at low temperatures, and the materials of Examples 5 and 6 exhibit a high loss coefficient at room temperature.

EXAMPLE 7

A resin composition was prepared from 100 parts by weight of a chlorinated polyethylene (“ELASREN 404B,” product of Showa Denko K.K., 40 wt. % in-chlorine content, 29 J/g in the degree of crystallinity, hereinafter referred to as “CPE 5”) and 200 parts by weight of a chlorinated paraffin [“ENPARA K50,” product of Ajinomoto Fine Chemical Co., Ltd., 50 wt. % in chlorine content, 14 in average carbon atom number (containing at least 99% of compound having 12 to 50 carbon atoms), hereinafter referred to as “Enpara 4”]. The materials were kneaded at 100° C. using a roll kneader, and the composition was pressed at 120° C. to obtain a sheet of damping material having a thickness of 1000 μm.

EXAMPLE 8

A resin composition was prepared from 100 parts by weight of CPE 5, 200 parts by weight of Enpara 4 and 100 parts by weight of a chlorinated paraffin [“ENPARA 70,” product of Ajinomoto Fine Chemical Co., Ltd., 70 wt. % in the degree of chlorination, 26 in average carbon atom number (containing at least 99% of compound having 12 to 50 carbon atoms), hereinafter referred to as “Enpara 5”]. The materials were kneaded at 100° C. using a roll kneader, and the composition was pressed at 120° C. to obtain a sheet of damping material having a thickness of 1000 μ.

EXAMPLE 9

A resin composition was prepared from 100 parts by weight of a chlorinated polyethylene (40 wt. % in chlorine content, 10 J/g in the degree of crystallinity, hereinafter referred to as “CPE 6”) obtained by post-chlorinating a high-density polyethylene by the water suspension process, and 200 parts by weight of Enpara 1. The materials were kneaded at 100° C. using a roll kneader, and the composition was pressed at 120° C. to make a sheet of damping material having a thickness of 1000 μm.

EXAMPLE 10

CPE 6 (100 parts by weight), 200 parts by weight of Enpara 4 and 100 parts by weight of Enpara 5 were kneaded at 100° C. using a roll kneader to prepare a resin composition, which was pressed at 120° C. to make a sheet of damping material having a thickness of 1000 μm.

COMPARATIVE EXAMPLE 7

A resin composition was prepared from 100 parts by weight of a chlorinated polyethylene (“ELASREN 401A,” product of Showa Denko K.K., 40 wt. % in chlorine content, less than 2 J/g in the degree of crystallinity, hereinafter referred to as “CPE 7”) and 100 parts by weight of a chlorinated paraffin [“TOYOPARAX” product of Tosoh Corp., 40 wt. % in chlorine content, 26 in average carbon atom number (containing at least 99% of compound having 12 to 50 carbon atoms), hereinafter referred to as “Enpara 6”]. The materials were kneaded at 100° C. using a roll kneader, and the composition was pressed at 120° C. to obtain a sheet of damping material having a thickness of 1000 μm.

COMPARATIVE EXAMPLE 8

A resin composition was prepared from 100 parts by weight of a chlorinated polyethylene (“ELASREN 401,” product of Showa Denko K.K., 40 wt. % in chlorine content, less than 2 J/g in the degree of crystallinity, hereinafter referred to as “CPE 8”) and 200 parts by weight of Enpara 4. The materials were kneaded at 100° C. using a roll kneader, and the composition was pressed at 120° C. to obtain a sheet of damping material having a thickness of 1000 μm.

The damping materials obtained in Examples 7 to 10 and Comparative Examples 7 and 8 were evaluated by the following methods as to the peak value and peak temperature of loss tangent (tan δ) and slipping-down time. Table 3 shows the result of evaluation.

[Loss Tangent]

Using a viscoelasticity spectrometer (product of Iwamoto Seisakusho Co., Ltd.), the sheet of damping material prepared was checked for loss elastic modulus in tension under the conditions of measuring frequency of 50 Hz, sample length of 15 mm and strain of 20 μm over a measuring temperature range of −50 to 50° C., with the temperature raised at a rate of 3° C./min. The loss tangent (tan δ) was calculated by dividing the loss elastic modulus in tension (E″) by the storage elastic modulus in tension (E′) to determine the peak value thereof and peak temperature.

[Slipping-Down Time]

The sheet of damping material prepared was affixed to one surface of a stainless steel panel (0.5 mm in thickness) for lamination to obtain a damping material of the restraining type. The resulting material was cut to 10 cm square, and the cut piece was affixed to a gypsum plasterboard with the damping material sheet in contact therewith, the plasterboard having the restraining-type damping material affixed thereto was allowed to stand, as vertically supported, in an oven having a constant temperature of 60° C., and the time taken for the stainless steel panel portion of the restraining-type material to slip down 5 mm from the initial position was measured as “slipping-down time” for the evaluation of stability during use at a high temperature. TABLE 3 Material characteristics Chlorine Avg. C Degree Content atom of crystallinity Proportion and result of evaluation (%) number (J/g) Ex. 7 Ex. 8 Ex. 9 Ex. 10 Comp. Ex. 7 Comp. Ex. 8 CPE 5 40 — 29 100 100 — — — — CPE 6 40 — 10 — — 100 100 — — CPE 7 40 — Up to 2 — — — — 100 — CPE 8 40 — Up to 2 — — — — — 100 Enpara 1 50 14 — 200 200 600 200 — 200 Enpara 2 70 26 — — 100 — 100 — — Enpara 3 40 26 — — — — — 100 — Loss tangent Peak value 2.8 3.0 3.4 3.4 1.5 3.5 Peak temp. (° C.) −1.3 5.8 0.2 6.2 −5.4 4.9 Slipping-down time (hr) At least At least At least At 8 2 1000 1000 1000 least 1000

Table 3 reveals that the materials of Examples 7 to 10 are high in the value of loss tangent (tan δ), prolonged in slipping-down time and found to be suitable for use at high temperatures.

EXAMPLE 11

A chlorinated polyethylene [100 parts by weight, trade name “ELASREN 402NA,” product of Showa Denko K.K., 9.2 in SP value, at least 140° C. in melting point (unmeasurable because the decomposition temperature was lower)], 250 parts by weight of a chlorinated paraffin (trade name “TOYOPARAX 150,” product of Tosoh Corp., 9.3 in SP value, −35° C. in melting point) and 200 parts by weight of a chlorinated paraffin (trade name “ENPARA 70,” product of Ajinomoto Fine Techno Co., Ltd., 10.6 in SP value, 105° C. in melting point) were placed into a 6-inch roll (product of Irie Tekkousho Co., Ltd.) and kneaded at 100° C. The kneaded mixture was 15° C. in Tg. In this way, a damping resin composition was prepared. The composition was supplied at 120° C. to a space between soft aluminum foil (trade name “8079,” product of Sun Aluminum Kogyo Co., Ltd, 0.2 mm in thickness) and a PET film (0.012 mm in thickness, 10.8 in SP value) to form a damping resin layer having a thickness of 1.5 mm and sandwiched between the soft aluminum foil and the PET film. At least one surface of the aluminum foil was treated with a primer in advance, and the damping resin layer was affixed to the treated surface. Further affixed to the outer surface of the PET film at room temperature was an adhesive sheet [trade name “DOUBLE TACK #5762,” product of Sekisui Chemical Co., Ltd., 0.12 mm in thickness, 0° C. in Tg, 9.5 in SP value, at least 140° C. in melting point (unmeasurable because the decomposition temperature was lower)]. Release paper was affixed to the outer surface of the adhesive resin layer. FIG. 1 shows a damping member of the restraining type thus obtained. Indicated at a in the drawing is the soft aluminum foil, at b the damping resin layer, at c the PET film, at d the adhesive resin layer, and at e the release paper.

EXAMPLE 12

A damping member of the restraining type (soft aluminum foil/damping resin layer/adhesive resin layer/release paper) was prepared by the same procedure as in Example 11 with the exception of not using any PET film.

COMPARATIVE EXAMPLE 9

An acrylic acid ester copolymer [100 parts by weight, brand name “P-501A,” product of Mitsubishi Rayon Co., Ltd., at least 140° C. in melting point (unmeasurable because the decomposition temperature was lower)], 300 parts by weight of a chlorinated paraffin (trade name “TOYOPARAX 150,” product of Tosoh Corp., −35° C. in melting point) and 100 parts by weight of a chlorinated paraffin (trade name “ENPARA 70,” product of Ajinomoto Fine Techno Co., Ltd., 105° C. in melting point) were placed into a 6-inch roll (product of Irie Tekkousho Co., Ltd.) and kneaded at 140° C. The kneaded mixture was 15° C. in Tg. In this way, an adhesive resin composition was prepared. The composition was made into a film having a thickness of 0.12 mm to obtain an adhesive sheet.

A damping member of the restraining type was prepared by the same procedure as in Example 11 with the exception of using the adhesive sheet thus obtained in place of the adhesive sheet of Example 11, i.e., “DOUBLE TACK #5762” manufactured by Sekisui Chemical Co., Ltd.

Performance Test

The restraining-type damping member samples obtained in Examples 11 and 12 and Comparative Example 9 were tested for performance with respect to the following items.

a) Adhesion performance

The sample was cut into straps with a width of 20 mm, the cut piece was affixed to an SPC steel panel, and the resulting assembly was subjected to a 90° C. peel test using a universal tester (Model UCT-5T, product of Orientec Co., Ltd.) at 23° C. (room-temperature tack) and 0° C. (low-temperature tack) under the condition of 300 mm/min.

b) Migration of liquid component

The sample was held in an oven at 80° C. for 2 weeks and visually checked for the oozing of the liquid component to the adhesive surface.

Table 4 shows the test result obtained. TABLE 4 Room-temp. Low-temp. Migration of Tack Tack Liquid component Example 11 20.0N 41.8N ◯ Example 12 19.5N   38N X Comp. Ex. 9 18.5  3.3N ◯ ◯: No liquid migrated. X: liquid migrated.

EXAMPLE 13

A chlorinated polyethylene (100 parts by weight, trade name “ELASREN 402NA,” product of Showa Denko K.K., 9.2 in SP), 250 parts by weight of a chlorinated paraffin (trade name “TOYOPARAX 150,” product of Tosoh Corp., 9.3 in SP), 200 parts by weight of a chlorinated paraffin (trade name “ENPARA 70,” product of Ajinomoto Fine Techno Co., Ltd., 10.6 in SP), 400 parts by weight of calcium carbonate (“R JUTAN,” product of Maruo Calcium Co., Ltd.) and 10 parts by weight of a tin-type thermal stabilizer (trade name “STANN RC-680B,” product of Sankyo Yukigousei Co., Ltd.) were placed into a 6-inch roll (product of Irie Tekkosho Co., Ltd.) and kneaded at 140° C. to prepare a damping resin composition.

The composition was supplied at 150° C. to a space between hard aluminum foil (trade name “JIS 8079,” product of Sun Aluminum Kogyo Co., Ltd, 0.2 mm in thickness) and a PET film (0.012 mm in thickness), the aluminum foil being coated over at least one surface thereof with a primer comprising a vinyl chloride-vinyl acetate copolymer (9.5 in SP), whereby a damping resin layer was formed which was 1.5 mm in thickness and sandwiched between the hard aluminum foil and the PET film. In this way, the damping resin layer was affixed to a restraining layer provided by the hard aluminum foil over the surface of the layer coated with the primer. Further affixed to the outer surface of the PET film at room temperature was an adhesive sheet (trade name “DOUBLE TACK #5762,” product of Sekisui Chemical Co., Ltd., 0.12 mm in thickness). Thus, a restraining-type damping member (restraining layer/damping resin layer/PET film/adhesive resin layer) was obtained.

COMPARATIVE EXAMPLE 10

A restraining-type damping member was prepared by the same procedure as in Example 13 with the exception of using hard aluminum foil having no primer coating, in place of the aluminum foil of Example 13.

Performance Test

The samples of restraining-type damping members obtained in Example 13 and Comparative Example 10 were tested for performance with respect to the following items.

a) Adhesion Performance

The sample was cut into straps with a width of 20 mm, and the cut piece was tested by tearing the restraining layer and the damping resin layer apart at 23° C. under the condition of 300 mm/min using a universal tester (Model UCT-5T, product of Orientec Co., Ltd.) to measure the adhesion strength at the interface.

b) Interface peel at rough surface

The sample was cut into straps with a width of 20 mm, and the cut piece was affixed to a steel pipe having a diameter of 150 mm on the inner surface thereof and visually checked for interface peel.

Table 5 shows the test result obtained. TABLE 5 Interface peel at rough Adhesion performance Surface Example 13 Break in resin material No (unmeasurable) Comp. Ex. 10 8.85N Yes

Table 5 shows that the restraining-type damping material of Example 13 is satisfactory-with respect to both items.

EXAMPLE 14

FIG. 2 shows a tone improving structure for acoustic systems according to the twelfth feature of the invention, as it is embodied for vehicle acoustic systems (car audio systems). The tone improving structure 1 has a secondary sound deadening sheet 3 affixed to a door 2 of a vehicle body, a speaker 9 being mounted on the door 2. The door 2 has an outer steel panel 4, inner steel panel 5 and lining 6. According to the present embodiment, the secondary sound deadening sheet 3 is affixed to the inner surface of the inner steel panel 5 approximately over the entire area thereof except the speaker 9 and to the outer surface of the lining 6 approximately over the entire area thereof as shown in FIG. 2. Although not shown, the sheet 3 is affixed to the outer steel panel 4 on the surface thereof facing the rear side of the speaker 9.

The secondary sound deadening sheet 3 is a laminate which is composed of a sheet of damping material 7 comprising a damping material resin composition, and a restraining member 8 comprising a thin aluminum plate. The sheet 3 is positioned with the restraining member 8 on the outer side (not to be intimately contacted), and is held in intimate contact with the steel panels 4, 5 and the lining 6 by virtue of the adhesion of a double-faced adhesive tape (not shown). The inner surface of the inner steel panel 5 and the outer surface of the lining 6 have indented or protruding curved portions, whereas since the restraining member 8 is in the form of a thin aluminum plate, the secondary sound deadening sheet 3 can be shaped in conformity with these curved portions in intimate contact therewith. The portions to which the sheet 3 is to be affixed are not limited to those described above; the sheet 3 may be affixed to the inner surface of the outer steel panel 4 approximately over the entire area thereof. The inner steel panel 5 and the lining 6 may have portions to which the sheet 3 will not be affixed when so required. The sheet 3 is applicable not only to the door 2 but also to metal portions or synthetic resin portions of the ceiling or floor in conformity therewith. In the case where the speaker of the vehicle acoustic system is to be mounted on the door with the lining 6 removed, it is desirable to affix the sheet 3 to the inner steel panel 5 and the lining 6 as illustrated in view of ease of the work.

EXAMPLE 15

A chlorinated polyethylene (100 parts by weight, trade name “ELASREN 402NA,” product of Showa Denko K.K., 40 wt. % in chlorine content), 250 parts by weight of a chlorinated paraffin (product number “E500,” manufactured by Asahi Denka Co., Ltd., 50 wt. % in chlorine content, 14 in average carbon atom number, 99 wt. % of compound having 12 to 16 carbon atoms), 200 parts by weight of a chlorinated paraffin (trade name “ENPARA 70,” product of Ajinomoto Fine techno Co., Ltd., 70 wt. % in chlorine content, 26 in average carbon atom number, 99 wt. % of compound having 20 to 50 carbon atoms) and 400 parts by weight of calcium carbonate serving as a filler were kneaded in a roll kneader to obtain a resin mixture, which was then pressed at 120° C. to prepare a sheet of damping material 7 having a thickness of 1.5 mm. The kneaded resin mixture was 2.7 in loss tangent (tan δ). A thin 0.2-mm aluminum plate 8 (70 GPa in modulus of elasticity) serving as restraining member was affixed to the sheet of damping material 7 to make a secondary sound deadening sheet 3. This sheet was 0.23 in loss coefficient. A double-faced adhesive tape (trade name “DOUBLE TACK TAPE #5762,” product of Sekisui Chemical Co., Ltd.) was used for affixing. A plasticizer migration preventing film 22 comprising a 40-μm PET film was provided between the sheet of damping material 7 and the double-faced adhesive tape 21 as shown in FIG. 6. For use in an actual vehicle (COROLLA FIELDER), the secondary sound deadening sheet 3 was affixed to the inner steel panel 5 of the door 2 and the lining 6 thereof.

EXAMPLE 16

The same procedure as in Example 15 was performed except that the sheet of damping material was affixed to each of the set of doors 2 of COROLLA FIELDER, the damping material sheet portions on the doors being positioned upright as spaced apart by 1.7 m.

COMPARATIVE EXAMPLE 11

No secondary sound deadening sheet 3 was affixed to the door 2.

COMPARATIVE EXAMPLE 12

The same procedure as in Example 13 was performed with the exception of changing the amount of the chlorinated paraffin (product number “E500,” manufactured by Asahi Denka Co., Ltd., 50 wt. % in chlorine content, 14 in average carbon atom number, 99.wt. % of compound having 12 to 16 carbon atoms) to 250 parts by weight, changing the amount of the chlorinated paraffin (trade name “ENPARA 70,” product of Ajinomoto Fine techno Co., Ltd., 70 wt. % in chlorine content, 26 in average carbon atom number, 99 wt. % of compound having 20 to 50 carbon atoms) to 100 parts by weight and using a 0.05-mm thin aluminum plate (70 GPa in modulus of elasticity) as the restraining member. The kneaded resin mixture was 1.5 in loss tangent (tan δ), and the secondary sound deadening sheet was 0.05 in loss coefficient.

For Example 15 and Comparative Example 11, a microphone 12 is installed at a position corresponding to the position of the ear of the driver in a driver's seat 11 as shown in FIG. 3. For Example 16 and Comparative Example 12, a microphone 12 is installed as positioned 0.4m away from one of the speakers. The secondary sound deadening sheets are evaluation by an evaluation method A and an evaluation method B described below.

Evaluation Method A

Reproducibility of sound volume: This method determines whether the ratio between the input sound volume recorded on a reproduction medium (CD) and the output sound volume reproduced by the speaker is 1:1. Sounds of 0 dB, -5 dB, -10 dB and −15 dB are input at different frequencies to measure the slope of an expression representing the relationship between the input sound volume and the output sound volume.

Evaluation Method B

Diminution of harmonics: In the case where sounds of different frequencies are reproduced, this method determines to what extent the second harmonic and third harmonic, which are sounds extraneous to such a sound, can be diminished. When a pure sound is input, the volume of a harmonic produced at the same time is measured.

Example 15 and Comparative Example 11 were evaluated with the results given in FIGS. 4, 5 which show the reproducibility of sound volumes and the effect to diminish the second harmonic, respectively.

Example 16 and Comparative Example 12 were evaluated with the results given in FIGS. 7 and 8, which show the reproducibility of sound volumes and the effect to diminish the second harmonic, respectively.

FIG. 4(a) shows the common relationship between the input sound volume and the output sound volume. When the output sound volume is in 1:1 relationship with the input sound volume, the theoretical slope is 1. In the case where the reproduced sound volume increases (sound amplification) as the sound increases, the slope becomes greater than 1, while when the reproduced sound volume diminishes (sound attenuation) as the sound increases, the slope becomes smaller than 1. For example, in the case where a sound in a low frequency range is amplified and a sound in a medium frequency range is attenuated by increasing the sound volume, tone varies with an increase or decrease of the sound volume, hence undesirable. The slope was determined at varying input signal frequencies, with the result shown in FIG. 4(b) for Example 15 and Comparative Example 11 and in FIG. 7 for Example 16 and Comparative Example 12. These drawings show that the range of a low frequency to a medium frequency (80 to 31.5 Hz) includes frequencies at which the slope is nearly 1.1 and those at which the slope is smaller than 0.9, in the absence of the secondary sound deadening sheet. However, in the case of Examples 15 and 16, the slope is almost nearly 1.0 and even the smallest slope is greater than 0.9 in a lower to high frequency range (50 to 12500 Hz). Thus, the secondary sound deadening sheets of Examples 15 and 16 are excellent in the reproducibility of sound volume over the different frequency ranges, especially achieving improvement in sound volume reproducibility especially over the lower to medium frequency range as compared with the absence of the secondary sound deadening sheet.

The sound pressure level of a harmonic was determined at varying input signal frequency with the result shown in FIG. 5 for Example 15 and Comparative Example 11, and in FIG. 7 for Example 16 and Comparative Example 12. These drawings show that the sheet of Example 15 greatly diminishes (about 20 dB) the harmonic component in a low frequency range (80 to 200 Hz) wherein the sound pressure level of the harmonic is greatest in the case of Comparative Example 11, and that the sheet of Example 16 also greatly diminishes (about 10 to 20 dB) the harmonic component in a lower frequency range (31.5 to 500 Hz) wherein the sound pressure level of the harmonic is greatest in the case of Comparative Example 12. It is seen that the sheet according to the twelfth feature of the invention improves the reproducibility of the original sound by diminishing the harmonic especially in the lower frequency range. Thus, the sheet of the invention diminishes the harmonic in the lower frequency range to thereby enhance the reproducibility of the original sound.

INDUSTRIAL APPLICABILITY

The present invention provides damping members of the restraining type suited, for example, to use in houses, apartment buildings, office building and like residential buildings, expressway, elevated bridges, railroad tracks and various like structures, motor vehicles, railroad cars, vessels and various vehicles, and also in household electric appliances and office automation appliances, for diminishing the vibration or oscillation and noise to be produced, damping material resin compositions for preparing such damping members, and damping materials comprising the composition.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view showing the layer structure of a restraining-type damping member prepared in Example 11.

FIG. 2 is a diagram showing an embodiment of tone improving structure of the invention for acoustic systems.

FIG. 3 is a diagram showing a device for use in an actual vehicle for evaluating a tone improving structure of the invention for acoustic systems.

FIG. 4 includes graphs showing an effect of the tone improving structure of the invention for acoustic systems.

FIG. 5 is a graph showing another effect of the tone improving structure of the invention for acoustic systems.

FIG. 6 is a diagram showing a preferred embodiment of tone improving structure according to the invention.

FIG. 7 is a graph showing an effect of another tone improving structure of the invention for acoustic systems.

FIG. 8 is a graph showing another effect of the same tone improving structure of the invention for acoustic systems.

DISCRIPTION OF REFERENCE NUMERALS OR SYMBOLS

-   1: tone improving structure for acoustic systems -   2: door -   3: secondary sound deadening sheet -   5: inner steel panel -   6: lining -   7: sheet of damping material -   8: restraining member -   21: double-faced adhesive tape -   22: PET film (plasticizer migration preventing film) -   a: soft aluminum foil -   b: damping resin layer -   c: PET film -   d: adhesive resin layer -   2: release paper 

1. A damping material resin composition comprising 100 parts by weight of a thermoplastic resin having a chlorine content of 20 to 70 wt. % and a weight average molecular weight of at least 400,000, and 100 to 1000 parts by weight of a chlorinated paraffin having a chlorine content of 30 to 75 wt. % and 12 to 50 carbon atoms.
 2. A damping material resin composition comprising 100 parts by weight of a thermoplastic resin having a chlorine content of 20 to 70 wt. %, 200 to 1000 parts by weight of a chlorinated paraffin having a chlorine content of 30 to 75 wt. % and a number average carbon atom number of 12 to 50, and 300 to 1000 parts by weight of an inorganic filler.
 3. A damping material resin composition comprising a thermoplastic resin having a chlorine content of 20 to 70 wt. % and a degree of crystallinity of at least 5 J/g as measured by DSC, and a chlorinated paraffin having a chlorine content of 30 to 75 wt. % and 12 to 50 carbon atoms.
 4. A damping material resin composition according to any one of claims 1 to 3 wherein the chlorinated paraffin contains 10 to 70 wt. % of a chlorinated paraffin having a chlorine content of at least 70 wt. %.
 5. A damping material comprising a damping material resin composition according to any one of claims 1 to
 3. 6. A damping laminate comprising a damping material according to claim 5, and a restraining member laminated to one surface of the damping material.
 7. A damping member of the restraining type comprising a damping material made from a damping material resin composition according to any one of claims 1 to 3, a restraining member laminated to one surface of the damping material, and an adhesive resin layer laminated to the other surface of the damping material.
 8. A damping member of the restraining type according to claim 7 wherein the difference between the glass transition temperature (Tg) of the damping resin layer and the Tg of the adhesive resin layer is at least 10° C.
 9. A damping member of the restraining type according to claim 7 wherein a plasticizer migration preventing film is interposed between the damping resin layer and the adhesive resin layer so as to separate these layers, and the difference between the SP value of the film and the SP value of all components having a melting point of up to 80° C. and included among the components of the damping resin layer and the adhesive resin layer is at least
 1. 10. A damping member of the restraining type according to claim 7 wherein the restraining layer is coated with a primer at least over a surface thereof adjacent to the restraining resin layer.
 11. A damping structure wherein a restraining-type damping member according to claim 10 is affixed to a rough surface of a vibrating body.
 12. A tone improving structure for acoustic systems wherein a secondary sound deadening sheet comprising a damping material made from a damping material resin composition according to any one of claims 1 to 3, and a restraining member laminated to one surface of the damping material is affixed to at least one portion of a peripheral device of the acoustic system with the damping material.
 13. An acoustic system tone improving structure according to claim 12 wherein the damping material is affixed to the peripheral device of the acoustic system with a double-faced adhesive tape, with a plasticizer migration preventing film interposed between the damping material and the adhesive tape.
 14. An acoustic system tone improving structure according to claim 12 wherein the damping material comprises a damping material resin composition at least 2.5 in the peak value of loss tangent (tan δ), and the restraining member is at least 1 GPa in modulus of longitudinal elasticity. 